Reactive pickup for vehicle control system



May 10, 1966 D. E. ATKINSON 3,250,983

REACTIVE PICKUP FOR VEHICLE CONTROL SYSTEM Original Filed Nov. 30. 1960 2 Sheets-Sheet l PHASE INVERTER 65 62 b INVENTOR.

DUANE E. ATKINSON F/G. 5 BY ATTORNEYS United States Patent 3,250,983 REACTIVE PICKUP FOR VEHICLE CONTRGL SYSTEM Duane E. Atkinson, 136 Newton Drive, Burlingarne, Calif. Original application Nov. 30, 1960, Ser. No. 72,645, now Patent No. 3,156,989, Nov. 17, 1964. Divided and this application Sept. 29, 1964, Ser. No. 400,073

4 Claims. (Cl. 323-53) This application is a division of my copending application Serial No. 72,645 filed on November 30, 1960, now

v US. Patent 3,156,989.

This invention relates generally to a reactive pickup for vehicle control systems and more particularly to a reactive pickup providing dual axis information.

In digging or leveling a bed in preparation for paving of road beds, canals, ditches and the like, it is necessary that the grading be even and accurate. It is well known that specifications for the paving are determined from several factors, among which is the finished elevation of the paved surface and the thickness of the paving. Consequently, the road bed must be below the desired finished road surface at least a distance equal to the specified thickness of the paving. It is realized that in actual construction, large amounts of material are employed. If the bed has been prepared too deep, the additional thickness of the paving material to bring the pavement up to the required elevation creates a large additional expense on the contractor.

In laying the pavement, control of its upper surface with respect to the bed surface is necessary. Otherwise, the pavement thickness may exceed specifications and create additional expense. On the other hand, if the finished pavement surface does not conform to the specified grade, the contractor may have to tear the pavement up and re-lay the pavement, again incurring substantial costs.

' By present methods, the bed is roughly graded by bulldozers or other such equipment to a preliminary level. Subsequently, a line is stretched and suspended along the road bed by surveyors. The line notonly indicates the general elevation of the bed but is, in addition, the reference for the actual. level of the desired surface. Using the line as a guide, the bed is again graded keeping a predetermined distance below the line.

This finished leveling and paving has been accomplished in the past by the operator of the final grading apparatus observing the line and visually keeping the proper position of the cutting blade or machine. More recently, advances have been made in the art wherein leveling may be accomplished in an automatic or semi-automatic operation. In some of these operations, levers are dis-. posed about the stretched line and serve to contact the line and mechanically activate a switch or adjusting leveling equipment or paving apparatus, as the case may be. Although such a system is definitely an advance in the art, it has several disadvantages. The flexing of the stretched line is inherent in applying force to throw the switch as is the actual movement of the arm in order 4 to activate the switch. Each of these deficiencies causes an error. Such errors, although small in themselves, create considerable expense on the contractor due to the large amount of materials involved in laying the pavement.

It is, therefore, an object of this invention to provide an improved reactive pickup for equipment control systerns.

It is a more particular object of this invention to provide an improved reactive pickup wherein a stretched electrically conductive energized line, indicative of the finished surface, is utilized.

arsena s Patented May 10, 1966 It is still another object of this invention to provide a reactive pickup for equipment or vehicle control system which provides dual axis information.

These and other objects of the invention will become more clearly apparent upon reading the following description in conjunction with the accompanying drawing:

Referring to the drawings:

. FIGURE 1 is a perspective view of grading equipment in operation;

FIGURE 2 is an enlarged view of a portion of FIG- URE 1 showing the novel reactive pickup in accordance with the invention;

FIGURE 3 is an enlarged view of the reactive pickup;

FIGURE 4 is a schematic block diagram of an electrical circuit used in conjunction with the reactive pickup of the present invention for providing information respecting one axis;

FIGURE 5 is a schematic block diagram of an electrical circuit used in conjunction with the reactive pickup of the present invention to provide information respecting the other axis; and

FIGURE 6 is a schematic diagram of the phase detector.

Referring to FIGURE 1, an electrically conductive line 11 is shown stretched between the posts 13. The line 11 is grounded at each end thereby forming a closed loop with ground. A grading tractor 19 is shown in operation adjacent to the line 11 in the road bed 21. The tractor includes wheels or tracks which engage the ground and support a cutting blade 23 and a final leveling blade 25, which are in fixed relationship with each other to operate at approximately the same level. The working means or blades which form the desired surface are adjustably supported with respect to the ground engaging means. A pickup 27 is disposed about the line 11. The pickup is aifixed to but insulated from the blade and serves to provide a reactive signal for blade adjustment in a manner to be described hereinafter.

The tractor 19 may include an electromagnetic wave radiator 28 disposed adjacent the line 11 but separated from the pickup 27. The radiator serves to induce a current in the loop including the line 11 and ground. A current also may be induced in the line by employing a ground based generator directly connected thereto.

Referring to FIGURES 2 and 3, it is seen that the pickup 27 is generally disc-shaped with a slot extending upwardly from the bottom thereof and terminating above the center. .The pickup is carried by the equipment in the illustrated embodiment. The pickup includes a disc 31 made of plastic or other suitable material. Reactive elements embedded therein may be disposed at 90 intervals at from the horizontal. The spacing of the reactive elements and the slot 33 are such as to permit the passage of the post 13 therethrough such that the line 11 may occupy that area in the center of the disc 31. It is to be understood, however, that the reactive elements may be disposed at any angle with respect to the horizontal and that the signals can be processed to give the desired data. This is apparent since it merely involves a rotation of axis by changing the magnitude of signals by the sine or cosine of the angle and combining them algebraically, as required.

Referring more particularly to FIGURE 3, the reactive elements shown are inductors 35-38. It is seen that the diametrically opposed inductors 35 and 37 .are serially connected and have terminals 41 and 43. Likewise, the diametrically opposed inductors 36 and 38 are serially connected and have the terminals 45 and 47. The inductors are, of course arranged so that they are inductively coupled to the magnetic field which surrounds the line 11 as a result of the current flowing in the line.

In the embodiment of the pickup shown in FIGURE 3, the slot 33 is disposed in the bottom of the disc 31. It is apparent that if the posts 13 are arranged other than vertical, the opening 33 should be disposed in such a manner as to receive the posts. The reactive elements may be disposed so as not to interfere with the slot and still provide the necessary signal energy as described above. Moreover, the slot 33 may be disposed in a horizontal plane whereby the line 11 enters the pickup through the side.

FIGURE 4 shows a schematic block diagram of one embodiment of the invention utilizing the inductive reactance pickup. As seen, the output of the serially connected coils 36 and 38 is applied through the terminal 47 and amplifier 56 to a phase detector 57. Likewise, the outputs of the series inductors and 37 are applied through an amplifier 58 to a phase detector 59. A phase reference signal appearing across inductor 36 is applied through the terminal 49 and amplifier to both the phase detectors 57 and 59. The output of the phase detector 57 is applied through the terminals a and 60b across the resistor 61, while the output of the phase detector 59 is applied through the terminals 62a and 62b across the resistor 63. The resistors 61 and 63 are serially connected and the extremities of the series connection are connected to the output terminals and 67. A source of alternating current voltage 69 is shown coupled to the line 11 by the reactance 71. The signal source 69 may be coupled to the line 11- by reactive coupling means located on the vehicle in proximity to the line but spaced from the pickup device 27 as schematically illustrated in FIGURE 1. The alternating current voltage source 69 may also be ground based and directly connected to the line.

In operation, the high frequency current flows in the loop including the line'11 and ground. This current createselectromagnetic fields which surround the line and are coupled to the inductors 35-38. The inductors 36 and 38 are wound so as to have induced therein signals of opposite phase. The inductors 35 and 37 are likewise wound to have induced therein signals of opposite phase.

If the line 11 is disposed closer to the inductor 36, a greater voltage will be induced in that inductor than in the inductor 38. Consequently, the overall voltage induced in the series combination including the inductors 36 and 38 will have a phase representative of that in the inductor 36, keeping in mind that the phase differences between the inductors 36 and 38 are 180.

The phase reference signal may be derived in any manner which is indicative of the phase applied. Thus, the signal appearing across one of the inductors such as 36 may be utilized as a reference signal. Alternatively, the reference signal may be derived directly from the signal supply 69.

' Thus, it is seen that if the predominant phase of the series inductors 36 to 38 is similar to the phase of the reference signal, the voltage output of the phase detector 57 will be of one polarity and will appear across the resistors 61. This polarity indicates that the line 11 is closer to the inductor 36 than to 38. Conversely, if the overall phase characteristic of the series inductor combination is opposite to that of the reference source, the voltage output will be of the opposite polarity and will appear across the resistor 61. This will indicate that the line 11 is closer toinductor 38 than to 36.

Referring simultaneously to FIGURES 3 and 5, if the line 11 is located above its center position as shown in FIGURE 3, a greater voltage will be induced in the inductors 35 and 38. The reference signal in the example shown is taken from the inductor 36. The voltage phase output under these conditions will be represented across the resistor 61 by a positive D.-C. voltage Likewise, the predominant voltage of the series combination including the inductors 35 and 37 will be that of t the inductor 35. The inductors 35, 37 are wound in the same sense as 38, 36, respectively. This voltage is applied to the phase detector 59 along with the reference voltage to derive a positive D.-C. voltage across the resistor 63.

The series combination of resistors 61 and 63 serve to add the outputs of the phase detectors 57 and 59thereby giving an overall voltage across the terminal 65 and 67 of plus-plus This overall voltage may be applied to a servo or solenoid unit which activates the controlsto the associated equipment. When the equipment has been re-positioned, the reactive pickup is repositioned with the line centered in the horizontal plane between the pickups 35, 38 and 36, 37.

It is obvious that if the line 11 is located below the center, the outputs of each of the phase detectors will be a negative D.-C. voltage. The total of the D.-C. voltages across the resistors 61 and 63, then, will be minus-minus and may serve to re-position the machine unti the pickupis again entered.

If the line 11 is located in any position along the horizontal center of the pickup 27, the sum of the phase detector outputs will be zero. This can be seen by realizing that the inductors 35 and 36 are wound to produce opposite outputs from the phase detectors 57 and 59 when the line 11 bears the same relation to each of them. Thus, when the sensor is operating to detect position errors in one axis, it is not affected by position in the other axis.

If, rather than adding the outputs of the phase detectors 57 and 59, these are subtracted, errors in the other axis are detected. Thus, again referring to FIGURES 3 and 5, if the line 11 were located to the right of center as shown in FIGURE 3, a greater voltage will be induced in the inductors 35 and 36. Here again, since the inductor 35 has a greater portion of induced voltage, the voltage at the resistor 63 will be plus However, the output of the phase comparator 57 will be the opposite of that in the previous example and the voltage on-the resistor 61 would ordinarily be minus thus making the sum voltage zero. To subtract, a phase in- I verter may be inserted between the output of one of the phase detectors, for example, the inverter 66, as shown in FIGURE 5. The voltage across the resistor 61 will be reversed and will also be plus Consequently, here again, the overall output across the terminals 65 and 67 will be plus-plus It is seen, therefore, that the subtraction circuit may be utilized to steer the vehicle in a horizontal direction while the addition process may be utilized to adjust the equipment in a vertical direction.

Subtraction may also be accomplished by reversing one of the pairs of output terminals 60a and b or 62a and b, or by reversing the polarity of diodes 79 and 85.

It is obvious that a converse arrangement may be utilized whereby the addition process is utilized to steer the vehicle while the subtractive process is utilized to adjust the blade. This variation may be accomplished merely by changing the sense of the windings in one of the series combinations of inductors.

FIGURE 6 is a schematic diagram showing the operation of the phase detector 57. It will be understood that the Phase detector 59 operates in a similarmanner. As is seen, the overall output of the series inductors 36 and 38 is connected across the primary 73 of the transformer 75. The reference signal from the pickup is applied to the center tap ofthe secondary 77 of the transformer 75. One side of the secondary 77 is coupled to ground through the diode 79 and the parallel combination of the resistor 81 and capacitor 83. The other side of the sec ondary 77 is coupled to ground through the diode 85 and the parallel combination of. the resistor 87 and capacitor 89. The output terminals 60a and 60b are connected to the junctions of the diodes 79 and 85 with their respective resistors 81 and 87.

In operation, if the line 11 is disposed equidistant between the inductors 36 and 38, the voltage induced by the series combination of the inductors is self-cancelling and zero voltage appears at the primary winding 73. The reference voltage being applied to the center tap of the secondary 77 induces equal current through the diodes 79 and 85. Consequently, there is no voltage differential between the opposite sides of the secondary 77 or across the outputterminals 60a and 6017.

If, however, the line is disposed closer to one of the inductors 36 or 38, a predominant voltage of one phase will be induced across the transformer 75. If, for instance, the line is closer to the inductor 36, the induced voltage across the transformer 75 will, in the lower portion of the secondary 77, be aiding the reference voltage applied at the center tap thereby causing more conduction to the diode 79. At the same time, the induced voltage will be bucking the reference voltage at the center tap 77 in the upper portion of the secondary 77 thereby producing less current through the diode 85. Consequently, a voltage drop appears across the terminals 60a and 60b which is representative of the relative position of the line 11 in the pickup device 27.

I claim:

1. A reactive pickup of the type which is inductively coupled to an electrically energized line comprising first and second interconnected coils having at least a pair of output terminals, and non-magnetic means for supporting said coils on diametrically opposite sides of said line with their axis perpendicular thereto.

2. A reactive pickup as in claim 1 wherein said nonmagnetic means for supporting said coils comprises a flat member having a notch extending inwardly from the side to a region between said coils.

3. A reactive pickup of the type which is inductively coupled to an electrically energized line comprising a first pair of interconnected coils having at least a pair of outputterminals and a second pair of output coils having at least. a pair of output terminals, and non-magnetic means for supporting said two pairs of coils with a coil of each pair on diametrically opposite sides of said line with their axis perpendicular thereto.

4. A reactive pickup as in claim 3 wherein said means for supporting said coils comprises a flat member having a notch extending inwardly from the side to a region between said coils.

References Cited by the Examiner UNITED STATES PATENTS 1,569,723 1/1926 Dickinson 336174 X 1,724,973 8/1929 Shaun 32452 1,971,207 8/1934 Boyajian et al. 32348 X 2,860,304 11/1958 Hall 324-52 3,079,548 2/1963 Robinson 323109 LLOYD MCCOLLUM, Primary Examiner. 

1. A REACTIVE PICKUP OF THE TYPE WHICH IS INDUCTIVELY COUPLED TO AN ELECTRICALLY ENERGIZED LINE COMPRISING FIRST AND SECOND INTERCONNECTED COILS HAVING AT LEAST A PAIR OF OUTPUT TERMINALS, AND NON-MAGNETIC MEANS FOR SUPPORTING SAID COILS ON DIAMETRICALLY OPPOSITE SIDES OF SAID LINE WITH THEIR AXIS PERPENDICULAR THERETO. 